1. Field of the Invention
The present invention relates to a silicone impression material having high hydrophilicity, and more particularly to a silicone impression material of an addition reaction type having high hydrophilicity.
2. Background Art
Impression materials have been used since long before in a variety of oral treatment to assess oral conditions. Impression materials are essential to fabricate dental prosthetic appliances in various situations of dental treatment, particularly when a tooth substance is lost because of dental caries or an oral environment is otherwise diseased and thus needs adjustment, and in case of implant dentistry treatment or esthetic dentistry treatment which has become widespread in recent years.
In general, impression materials used to assess oral conditions are pasty viscous material, and cured by a variety of curing mechanisms to change into a gummy elastic material. In clinical situations, a pasty impression material is pressed onto a location, the impression of which is to be taken. After the impression material is held for a certain period, it is checked whether the impression material has changed into a gummy elastic material, and then the cured impression material is taken out of the oral cavity.
While various types of impression materials have been developed so far, alginate impression materials, agar impression materials, and silicone impression materials are mainly used today.
Among the alginate impression materials, alginate impression materials of a powder type containing alginate powder and cured when mixed with water were commonly used. In recent years, however, alginate impression materials of a paste-paste type having good preservation stability have been increasingly used. In Japan, in particular, the alginate impression materials are often used in combinations with the agar impression materials, and known as common impression materials for health insurance treatment.
The agar impression materials containing thermoplastic gel at high temperature is in the sol state and is galated to be cured as the temperature lowers. In Japan, in particular, the agar impression materials are often used in combinations with the alginate impression materials, and known as common impression materials for health insurance treatment.
The silicone impression materials contain two types of pastes, namely a base paste and a catalyst paste, which are kneaded with each other to be cured into a gummy elastic material. The silicone impression materials are roughly divided into a condensation type and an addition type depending on the curing mechanism. In recent years, the silicone impression materials of the addition type have been mainly used from the viewpoint of their high dimensional accuracy and the safety of their composition to human bodies.
The silicone impression materials of the addition type hardly change in dimensions after being cured, and there is almost no need to consider their changes in dimensions in an environment around room temperature. In this point, the silicone impression materials of the addition type are superior to the alginate impression materials and the agar impression materials. However, the silicone impression materials contain a siloxane polymer that is generally hydrophobic, and therefore are disadvantageously incompatible with wet tissues compared to the alginate impression materials and the agar impression materials. Normally, the oral cavity is in a wet environment, and it is difficult to completely dry a location, the impression of which is to be taken. If tissues in the oral cavity are completely dried, the oral cavity is no longer in its usual state, and is not suitable for impression sampling. A plaster modeling material is injected into the impression material taken out of the oral cavity. However, the silicone impression materials of the addition type are also less compatible with the plaster modeling material than the alginate impression materials and the agar impression materials.
In order to address such drawbacks, a variety of attempts have made to add hydrophilicity to the silicone impression materials, such as by adding a surfactant, by compositing a material having hydrophilicity, and by synthesizing a siloxane polymer having a hydrophilic group, as taught in the patent documents mentioned below.
Japanese Patent Application Publication No. 63-130510 (JP63-130510A) describes an example of a silicone impression material according to the related art. The publication discloses that hydrophilicity of the dental impression material can be enhanced by including a surfactant selected from polyol fatty acid ester based and ethoxylated ester based surfactants in a dental impression material containing a vinyl polydimethylsiloxane, a hydro-polydimethylsiloxane, a silica filler, a cyclic vinyl siloxane, a chloroplatinic acid complex, platinum black, and a plasticizer.
Japanese Patent No. 4090536 discloses a silicone impression material for dental impression that is highly elastic with large elastic strain and small permanent strain, that does not drip or tear during impression taking, and that is highly wettable with water. The silicone impression material disclosed therein is obtained by adding respective specific amounts of impalpable silica powder, a nonionic surfactant, and a methylphenyl polysiloxane to a silicone impression material of an addition polymerization type containing an organopolysiloxane having at least two aliphatic unsaturated hydrocarbon groups in a molecule, an organohydrogen polysiloxane having at least three hydrogen atoms directly bonded to a silicon atom in a molecule, a silicone-soluble platinum compound, and an inorganic filler.
Japanese Patent Application Publication No. 62-252706 (JP62-252706A) discloses an organopolysiloxane composition containing a silicone-polyether compound having a hydrophobic silicone portion and at least one hydrophilic polyether portion, to express hydrophilicity to wet tissues.
Japanese Patent Application Publication No. 2011-506612 (JP2011-506612A) discloses a dental impression material containing a curable organopolysiloxane polymer, a cross-linking agent compound capable of cross-linking the organopolysiloxane polymer, a catalyst capable of catalyzing the cross-linking reaction, a surfactant, and an F-containing compound, to express hydrophilicity both before and after being cured.
Japanese Patent No. 4154576 discloses combining a base polymer containing a curable organopolysiloxane containing 5 mol % or more of diphenyl siloxane units or 10 mol % or more of methylphenyl siloxane units with a polyether to obtain a highly hydrophilic curable material having a contact angle of 70° or less, in particular 65° or less, based on JIS R3257. Japanese Patent No. 4154576 further discloses that the obtained highly hydrophilic curable material is cured well even after a long period of storage because the polyether is not easily separated from the compound or the curable material, thereby suppressing variations in wettability with a water-based paint or in impression performance and showing superior hardening property.
Although the impression material according to Japanese Patent Application Publication No. 63-130510 (JP63-130510A) exhibits high hydrophilicity before being cured, the impression material does not reproduce a plaster model well, and the hydrophilizing agent adversely affects the physical properties for a dental impression material. Therefore, the impression material may not maintain desirable physical properties for a dental impression material, or has poor preservation stability.
Although the impression material according to Japanese Patent No. 4090536 exhibits high hydrophilicity before being cured, the impression material does not have high hydrophilicity after being cured, and may not reproduce details when plaster is injected.
Although the impression material according to Japanese Patent Application Publication No. 62-252706 (JP62-252706A) provides sufficient hydrophilicity after being cured, the impression material does not provide sufficient hydrophilicity before being cured, and may not produce details during impression sampling.
The impression material according to Japanese Patent Application Publication No. 2011-506612 (JP2011-506612A) is slow in expressing hydrophilicity, and may take time to become compatible with wet organisms in the oral cavity.
The impression material according to Japanese Patent No. 4154576 is slow in expressing hydrophilicity, and may take time to become compatible with wet organisms in the oral cavity.
The dental impression materials according to the related art taught in the patent documents mentioned above do not instantly express high hydrophilicity in the oral cavity before being cured, and do not exhibit high hydrophilicity when plaster is poured after being cured. Therefore, an impression that reproduces details of the oral cavity well may not be obtained immediately using the dental impression materials according to the related art.